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How did aviation industry come to know about the drastic difference in air pressure in high altitude?
After watching many documentaries about air plane crashes, it seems that aviation industry learned many of its lessons from disasters. For example, from the 2 mid-air explosion of de Havilland DH 106 Comet in 1950s they learned a lot about metal fatigue that can cause Explosive decompression. So, I'm curious to know how did the industry come to know about the drastic difference in air pressure that occurs in high altitude? Was the knowledge already there before an airplane was even invented?

It wasn't the fact that it was pressurised. It was the fact that the windows were square which is a bad design (we know now thanks to the extensive investigation) which concentrates the fatigue forces of repeated pressurisation/de-pressurisation cycles into the corners which eventually cracked and caused catastrophic fuselage failure.

@Simon Well I did say "metal fatigue that can cause Explosive decompression". The metal fatigue itself happens because the pressurized air continuously pushes the metal structure of the plane. The air is pressurized in the first place because air is thinner in high altitude. If the air was not thin, the accident wouldn't occur at all.

Errr.... AFAIK the change in air pressure is gradual, not "drastic". The difference could perhaps be called "drastic", but not the change.

Nobody's really answered the question of whether there were any accidents caused by pilot oxygen deprivation from high altitude flight, or even the first designs of high-flying planes took this into account.  Hillary didn't summit Everest until 1953, and I thought hypoxia wasn't well understood until after high-altitude flight was possible.

@PeterCordes Because no-one has asked the question.

@Simon: I thought the earliest flights to high altitude was where the OP was going with this, and the Comet crashes were just an example of one of the consequences of pressurised cabin designs.  On more careful reading, I see that didn't actually get asked.

@steveverrill "Disintegrated mid-air" would probably be a more accurate description than 'crashed.' Either way, it's something that's best avoided.

The decrease in air pressure is the chief reason why planes have a service ceiling. The existence of such a ceiling was discovered quite early on, empirically.

@Simon ('s first comment): The Comet 1's windows were rounded squares, and not all that much less round than most aircraft windows today.  The problem was the punch riveting used to attach them, not their shape.

The entire reason why the Comet broke up in midair is because they pressurized the plane in the first place.
It was known for a long time that air at high altitude was thinner. This can be experimentally verified by taking a barometer up to a mountain. This was first done in 1648 (and subject to hot debate regarding the nature of air) more than 250 years before the Wright brothers first flew.

Fun related fact: most smartphones these days come with a barometer, which is sensitive enough to notice the difference between air pressure at your head and your feet (no need to climb up a mountain these days).

@sanchises Interesting. I had forgotten about those being in phones. In a search just now I saw a couple of articles from last year saying that the iPhone was going to use the barometer to tell you your altitude... I'm curious how that's working out for them. :) Sounds like it would work great if you happen to have a standard atmosphere at your current location... and not so great otherwise. "Hmm... It's hot today... why did our house just move up 150 feet?"

@reirab I actually have an Android app (Sensitive Altimeter) that reads METAR data of an airport of choice and displays your altitude relative to that (with an aviation-style indicator if you like, although I guess "mom called" is not a good reason for entering restricted airspace).

Aside from mountaineering investigations, the service ceiling of WWII propeller-driven aircraft like the Spitfire was pushed up from about 34,000 feet to 45,000 feet, so the general effect of reduced air pressure on aircraft and engine performance was already known. Of course both civil and military aircraft were unpressurised before the start of jet-powered civil aviation (though there were some experiments with full-body pressurised suits, to avoid damaging the aircrew more than the plane at those altitudes).
I think the significant novelty was discovering the effect of cyclic stresses (a.k.a. "fatigue") in a new situation, namely of the order of 100 to 1000 loading cycles to failure. Before that, the most common design consideration was one loading cycle, where over-stressing caused immediate failure. With a suitably large safety factor and fortuitous choice of materials, that design criterion would also give an "infinite life" for high-cycle fatigue situations like rotating machinery (e.g. piston engines). New materials, plus lower safety factors driven by the need for minimum weight, discovered a new "cliff edge" for designers to "fall off" - and the history of engineering contains many examples of cliff edges being discovered by falling off them.

Most German high performance military planes of WWII had a pressurized cockpit. For example, all Me-109s with an even number behind the subtype letter had one (e.g. 109 G-6, 109 K-4).

Not to mention the Lockheed Constellation, the Boeing B-29, or the Boeing 307.  The latter was a pressurized passenger plane in service (in limited numbers) prior to WWII.

The range of air pressure from sea level to the maximum ceiling of modern aircraft was known even before the airplane was invented. The difference between the troposphere and stratosphere was discovered by balloon measurements by Teisserenc de Bort in 1902. Most passenger airlines fly in lower levels of the stratosphere. No planes can fly above the stratosphere.


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Are there specific regulations for airports near water bodies?
Are there any regulations that requires that international airports maintain a navigation channel deep enough to have access in case of an emergency when the airport runway ends near a body of water?

Yes, there are ICAO regulations requiring water rescue facilities. For example, from New marine rescue fleet launched at Auckland Airport:

Airports which have a significant proportion of aircraft movements over water are required by the International Civil Aviation Organisation (ICAO) to provide a specialist rescue facility, capable of an effective response in a marine area around the airport. Marine rescue craft are required to be able to transport sufficient flotation equipment to an accident site to support the number of people carried in the largest aircraft.

You can find this regulation in the ICAO Aerodrome Standards document:

Emergencies in difficult environments
9.1.14 The plan shall include the ready availability of and coordination with appropriate specialist rescue services
  to be able to respond to emergencies where an aerodrome is located close to water and/or swampy areas and where a significant
  portion of approach or departure operations takes place over these areas.
9.1.15 At those aerodromes located close to water and/or swampy areas, or difficult terrain, the aerodrome
  emergency plan shall include the establishment, testing and assessment at regular intervals of pre-determined response for the
  specialist rescue services.

Note that this does not necessarily require a navigation channel, as rescue operations can be primarily provided by hovercraft (as in Auckland).

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At what point does the throttle control RPM on a constant speed prop?
On an airplane with a constant speed prop, the prop lever typically controls the RPM (pitch) of prop, and the throttle controls the power, measured as Manifold Pressure ("MP"). However, at low power settings with the prop lever full forward, there is a point where the throttle control begins to act like a throttle on a constant pitch airplane where the throttle controls the RPM. This is the point that I'm asking about.
Does this point occur at the same MP on all aircraft? Conceptually I understand that when the prop is set to max RPM the prop will adjust pitch finer and finer as I reduce power until it gets to the point where it can't flatten out the pitch anymore as I continue to reduce power, then the RPM will begin to drop. Is this a point that is specific to engine/prop combination or is it adjusted by mechanic?

When the prop can no longer pivot in the hub.

This can only be adjusted to a point. At some point your blades are completely flat, any more and you'll basically go into "beta", which is something you don't want to do on an aircraft that doesn't explicitly support it.

Nah. There are stops built into props that only allow travel to a certain limit. Since the op includes MP in the question, we know he is not asking about turboprops, so beta is not relevant. The prop will hit the stops and the will be effected by the throttle at low and high rpm limits.

What happens is when you're on final and you move the prop to MAX RPM, the prop governor moves the blades finer until the RPM is at red line, then governs RPM there by adjusting blade angle as required.  As you reduce throttle, the governor moves the blades finer and finer trying to keep the RPM that has been set (maximum or redline RPM in this case).
As throttle is further reduced the blades hit the fine pitch limits of the propeller hub and can't go any finer, so the governor can't unload the engine any more to keep the RPM up.  As you continue to reduce throttle you basically now have a fixed pitch prop with very finely pitched blades and down comes the RPM.  As long as throttle is below the level that will speed the prop up above redline (or whatever the governor setting is), RPM will vary directly with throttle, like a fixed pitch prop engine.
Add power and RPM rises until it hits the governor setting, then the governor starts to coarsen pitch to load up the engine, to keep the RPM at the setting.
The point at which the prop "comes off the governor" is determined by the pitch limits of the blades within the hub.  The part the mechanic can adjust is the RPM set by the governor when the prop lever is at MAX, which is normally redline RPM +/-.

excellent exposition. thanks for posting this.

"Hitting the (pitch) limits" is formally called actuator saturation.  Google it yourself, because the results' comprehensibility depend strongly on your engineering background.

Well my answers are written for laypeople, not engineers, so I try to minimize engineer-speak.  Fine pitch limits, fine pitch stops, it's simply referring to a mechanical travel limit of something that moves.  No need to get too deeply into sematics.

Fine pitch limits, fine pitch stops... terms such as these work just fine for this 7,000-hour commercial seaplane pilot.  Thanks, John K.

@JohnK Great answer! My question is about the "fine pitch limits of the propeller hub" as you put it. Is that a point that is encountered at 1/2 throttle, or 2/3 throttle, or is there some other metric that is used?  I imagine that a more powerful engine installed on same prop/governer would reach the "fine pitch limit" at lower RPM.

It's the physical limit on the blade's rotation within the hub.  When it gets there depends on the torque being applied and it will vary. When torque is no longer sufficient to sustain the RPM at the fine pitch limit, RPM will start to drop. This will be at some fairly low manifold pressure and will also vary with airspeed, maybe between half and 1/3rd throttle, say between 15-20" MP (I haven't flown an airplane with a CS prop in some years so I can't remember). But if you have set the prop to MAX RPM, and RPM starts to drop below red line, you are there; the blades are as fine as they'll go.

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What are the Takeoff Minimums for aircraft operating under Part 91?
What are the IFR Takeoff Minimums for aircraft operating under Part 91?

According to the Instrument Procedures Handbook (FAA-H-8083-16A) page 1-8:

"Aircraft operating under 14 CFR Part 91 are not required to comply
  with established takeoff minimums. Legally, a zero/zero departure may
  be made, but it is never advisable."

Does that include only standard minimums, or does it also extend to minima prescribed under §97? James Albright says that pilots must still adhere to minima prescribed under §97 when operating under §91. There is substantial debate on this.

I was surprised by this when I learned it, and had to share. The statement in the handbook seems very clear and it was from the 2015 version.

James Albright argues essentially that the operation is also under §97, not only §91. A bit of a grey area, but I am inclined to disagree with him on this, as much as I respect his opinion and body of work as a whole.

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Are aircraft pilots required to fly runway heading for a certain distance?
If an aircraft rotates off the runway relatively quickly (runway mid-point for example), do pilots need to continue on the runway heading for a minimum distance before turning based on departure procedures? For example, for the Runways 31L/R CANARSIE climb at JFK, the established departure procedure is "Climbing left turn direct CRI VOR/DM". For this same procedure, can the departing aircraft proceed direct to CRI VOR/DM like the image below, if safely possible, or do they need to maintain runway heading till the runway is cleared?
Thanks!

Depends on the airport. Are you asking specifically about JFK?

The initial turn should be made at 400 feet AGL.
Unless otherwise specified in the departure procedure, the initial turn should be made when reaching an altitude of 400 feet above the runway elevation as specified in the AIM:

Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing restriction, until the minimum IFR altitude. A greater climb gradient maybe specified in the DP to clear obstacles or to achieve an ATC crossing restriction. If an initial turn higher than 400 feet above the departure end of runway elevation is specified in the DP, the turn should be commenced at the higher altitude. If a turn is specified at a fix, the turn must be made at that fix. Fixes may have minimum and/or maximum crossing altitudes that must be adhered to prior to passing the fix. In rare instances, obstacles that exist on the extended runway centerline may make an “early turn” more desirable than proceeding straight ahead. In these cases, the published departure instructions will include the language “turn left (right) as soon as practicable.” These departures will also include a ceiling and visibility minimum of at least 300 and 1. Pilots encountering one of these DPs should preplan the climb out to gain altitude and begin the turn as quickly as possible within the bounds of safe operating practices and operating limitations. This type of departure procedure is being phased out.

(AIM 5-2-6 Departure Procedures, emphasis mine)
The Canarsie climb at JFK does not include any special instructions for when to make the turn:

CANARSIE CLIMB: Climbing left turn direct CRI VOR/DME. Make turn east of
CRI R-039 (remain within JFK 4.5 DME), then via CRI R-176. Cross CRI 2 DME
or JFK R-253 at or above 2500, thence . . . .

(Kennedy Five Departure)
I would therefore start the turn at 400 feet. In principle, this would allow turning before reaching the far end of the runway, but only for a very good climb performance or a very long runway.

Had a note on the SID "do not turn before DER". Ashamed to say I spent 5 minutes looking for the DER vor on the chart :-)

Note also the recommendation/standard procedure is to cross the DER at least 35 feet above DER elevation, climb to 400 feet above DER before making turn, etc. To me that means that the pilot must continue to fly runway heading for at least as long as it will take them to reach the departure end of the runway, even if they reach 400 feet at midfield. Not quite sure how pilots would determine this if they immediately enter IMC...

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Sideslip vs Freestream Azimuth Angle
Why is the sideslip angle, $\beta$, defined as
$$\beta=sin^{-1}\left(\frac{v}{|{\bf v}|} \right)$$
and not the same as freestream azimuth angle $\psi$
$$\psi=tan^{-1}\left(\frac{v}{u} \right)$$
where ${\bf v}=u \hat {\bf b}_x+v \hat {\bf b}_y+w \hat {\bf b}_z$ is the airspeed of the aircraft in body coordinates, $\hat {\bf b}$, and $|\cdot|$ is euclidean norm of $\bf v$. $\psi$ can be interpreted as the angle between $\hat {\bf b}_x$ and the projection of $\bf v$ onto the bodies $x$-$y$ plane. What is the physical interpretation of $\beta$?
Thanks in advance!

Is it helpful to consider the case of knife-edge flight, i.e. flight at a 90-degree bank angle, with the side of the fuselage supporting most of the aircraft weight?

@quietflyer, thank you, it is a thought provoking suggestion but I am struggling to gain any insight from it haha

Likewise I am not familiar enough with this highly mathematical approach to provide you a quick answer--

Where did you find these definitions, please?

For $\beta$ see PDF page 341: https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.usntpsalumni.com/Resources/Documents/USNTPS_FTM_103.pdf&ved=2ahUKEwid7-fm9PjiAhWImOAKHZEVCTEQFjABegQIBRAL&usg=AOvVaw3t7J5ddx58KEAXnlur_Sib. I don't have a reference for the freestream azimuth $\psi$...but it seems to be how most people think of sideslip.

I think this answers my question. If anyone wants more details please let me know:

The sideslip angle, $\beta$, is the angle which the stability coordinate system needs to be rotated about the $z$ stability axis after being rotated by the angle of attack, $\alpha$, about the body $y$-axis. The sideslip angle is equal to the freestream azimuth angle $\psi$ when the angle of attack is zero.

Dispensing with the math, because it makes my head hurt...
Azimuth refers to geographic direction relative to a compass reference point, so azimuth angle refers to the deviation between the body's longitudinal axis and its horizontal path parallel to the earth's surface (heading vs track along the ground).
Sideslip angle refers to the deviation, referenced along the lateral axis of the body (parallel to the wings in other words), between the body's longitudinal axis and the airflow, independently of direction relative to the earth.


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What are reasonable values for the position of an airplane's center of gravity compared to that of its center of lift?
I understand that if the center of gravity is in front of neutral point, it is stable. If the center of gravity is behind the neutral point, it is unstable. Based on the diagram, is it implied that h (center of gravity) cannot be greater than 1? When h = 1, there will only be c (mean aerodynamic chord). What does it mean if h>1? Is it off the wing basically?

hnwb = 0.25 (typically)
When I solved a problem, my h value was greater than 1. Isn't that incorrect because it is off the wing?

Welcome back to Stack Exchange! What do you mean by "value for the center of gravity"? Isn't the center of gravity a point on the aircraft, not a number? I can only guess what you're trying to ask.

You can calculate the center of gravity in terms of mean aerodynamic chord.

I cannot find hnwb, h and hn in the diagram.

I've changed the picture, sorry.

So it sounds like you're saying that for the location of the center of gravity, 0 means the leading edge of the wing and 1 means the trailing edge? Am I understanding that right?

What do you mean by "neutral point"? I suggest you read the stability section on how it flies? to have an idea of how center of gravity position affects aircraft stability.

I edit the title to (i) transform it into a question (this is a Q&A site) and (ii) be more specific. If it does not reflect what you are asking for, feel free to edit it again.

@ManuH I don't think that's what the OP is asking. The OP is asking whether the neutral point can be aft of the mean aerodynamic chord. Typical NP is around 40-60% MAC.

@Jimmy feel free to correct.

@M.D. White  dig a little deeper into the definitions.  The aerodynamic center is not a directional stability "neutral point".  Static stability is set up with the CG ahead of the Center of Pressure (lift) and a bit of tail downforce.  Remember to consider forces on the entire plane.

I think what you're getting at is to set CG (there for CP) at wing aerodynamic center so change in AOA does not produce a pitching moment (with use of tail down force). Interesting concept, but, as long as CP and CG are in same spot, you don't get static stability (and extra trim creates more drag). I'm liking slats for lower speed pitch control application (less high AOA airflow interference)

On swept wings, that is

If I understand your question correctly, h is a fraction of mean aerodynamic chord c. That fraction can be >1. It could be that the aircraft is stable with a huge download on the tail.
The mean aerodynamic chord is an aid, to simplify calculations. It is not a hard limit for the equilibrium points. Whether the value is reasonable or not is hard to say without having seen the full problem to be solved.

Never seen an NP off the MAC. But maybe with tandem wing?

@Jimmy no I haven’t either, but it is not wrong by definition.

The reasonable value for center of gravity compared to the center of lift is a 2 part process in horizontal stabilizer design.  Set static stability aside for now.  For most efficient flight you want the main wing only generating lift.  Ideally, the horizontal stabilizer should be at 0 AOA, holding the wing in place at optimal Lift/Drag AOA.  Center of gravity is directly under Center of Lift.
Job 1 complete.
Now we want to introduce static stability, also known as speed stability.  This is extremely important when you are "low and slow" to avoid stalling.  It is a terrific safety feature even with computer assisted control.  So you move your TRIM tab to give a little bit of tail downforce and move your CG slightly forward as needed for adequate static stability. Job 2 done.
The 3rd function of the horizontal stabilizer is to pitch the nose down if the plane sinks, in order to avoid ever increasing AOA and unrecoverable "deep stall".  Here, within reasonable limits, the more area, the better.  Wedge or delta shaped designs are popular with birds.
So there is a difference between a horizontal stabilizer and a trim tab.  Champions of tiny
Hstabs should be aware of this (although a longer fuselage does also increase pitching torque).


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What could cause a lower manifold pressure at full power after an annual?
I recently completed the annual on my E33 Bonanza.  I notice on takeoff at full power that the MAP is about 1" less pressure than it was in the past at my home airport.  It is also about 1.5" less than ambient.  I notice less power slower Acceleration and lower climb rates.  Fuel flow looks normal.  Where else should I search and troubleshoot?

Are the actual airport and your home airport at the same elevation?

Due to the resistance of the air filter the MP should be about an inch less than ambient so what you are seeing seems about right.  If there was a leak in the intake manifold before the air filter (before the annual) then that might explain why your engine developed more power before (although the engine sucked in dirt).


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Are you mandated to use a Fault isolation manual when clearing a defect on an aircraft?
I operate a Bombardier Dash 8 Q400. I want to know if aircraft engineers are mandated to close or rectify a defect by only following the fault isolation manual (FIM). Can an engineer instead use his knowledge and experience of the systems to isolate the problem and resolve the defect?

what are FIM and AMM?

As a pilot or maintenance?

@ Manu H Fault Isolation Manual and Aircraft Maintenance Manual

It would seem to depend on the particular aircraft, and perhaps whether it's private or commercial.  AFAIK there's no such thing as a "fault isolation manual" for my Piper Cherokee.

Engineer, or FAA certified mechanic?  Hypothetical, or actual situation?  If actual, and if properly diagnosed, I don't see a problem.  I could be wrong, but I don't think technicians are bound to using checklists in the way aircrew are.  Now if they didn't use a reference and missed something, that's a totally different issue.

FIM contains procedures for both A/C systems (E.G. EICAS, ECAM, CPDS) messages and pilots/maitenance observations (e.g. smell of burning oil, windshield delamination).
All kind of reasonably possible faults should be covered by FIM.
Just simply use yor FIM preambule to determine if it specifies what to do when fault is not covered by FIM and to determine either mechanic judgement or OEM (A/C manufacturer)contact is requied in such case.
If such information is not included contact OEM.


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What is the highest service ceiling for turboprop airplane like a Cessna 425?
What is the highest service ceiling turboprop airplane,  that is fairly small, like maximum of 8 seats, and fairly cheap as well, not going over a million dollars. I looked at Cessna 425, and this plane has a service ceiling of 10km(33000ft), and this plane had the highest service ceiling, that fit the size and cost, that I could find.
So, basically , what plane out there has the greatest service ceiling, that  is small in size, like the Cessna 425, turboprop,  and cheap (under a million) ?

Are you asking about new cost? This is a really broad question, for example you may be able to find a used Lancair Evo for less than $1m...

@fooot I pretty much mean a plane of the size of Cessna 172 and Cessna 425. I am doing this for research purposes.

@abelenky Not sure if it matters to the op, but Turbocharged and Turboprops are pretty dissimilar.

Does it have to be a twin engine? Does it have to be turboprop?

The PA-46-500TP Malibu Meridian can climb to FL300 and you may be able to find a high time one for under a million.
Socata TBM has a quoted ceiling of 31,000 ft and you may be able to find an older TBM 700 high time airframe for in and around a million.
In the multi-engine category:
A PA-42 Cheyenne will put you up to just under 36,000 ft and can be had used for under a million.
A Beech King Air C-90 will get you up to 30,000 feet and can be found used on the lower end of the price spectrum.


text:
What are the advantages of electrical systems over pneumatic systems?
What are the advantages of using electrical systems as a alternative to pneumatic systems in the Boeing 787-9? Is it a maintenance advantage?

related: hydraulic vs pneumatic

Hydraulic vs Electric

Just on example: The energy taken from the engine as bleed air is contained in this bleed air as heat and as pressure. Now pipe this energy to someplace where it is needed, and the air will cool down and lose some of its pressure. Also, if you want adequate insulation and low transmission losses, the cross section for the piping will be substantial.
Compare this to taking the energy from the engine by a driveshaft turning a generator: Friction losses will be a few percent at most, energy conversion in the generator will be at above 90%, and transmission losses are low again if your cable cross section is sufficient. Note that the cables will be much thinner than any bleed air line would ever be.
Add to this the advances made in converting electrical energy between different voltages and frequencies, and it becomes clear that modern aircraft systems can be made more efficient when run electrically. The use of compressed, hot air was only a better choice when modern power electronics were not yet around.


text:
Can an aircraft be controlled after an ejection?
What kind of damage does the ejection process do to the inside of a cockpit or to the aircraft in general?
If ejection were accidentally triggered on the ground (i.e. the ejection wouldn't be followed by a hull damaging/destroying crash), would the damage be minimal enough that it could be flown again by simply installing a new seat and canopy, or would it have to go through a major inspection to ensure no additional damage was done to instruments, wiring, etc?

This question is not about aviation, since none of the ideas you mention are possible.  If you were to edit to simply ask what kind of damage does ejection do to the cockpit, it might be answerable.

I second @Simon's comment here, this is very hypothetical because you would not be able to hold onto the aircraft in the first place, let alone reach inside or open the canopy from outside. Rephrase the question to the final part of the aircraft being maneuverable after ejection and it can be salvaged.

Fair enough. Thanks.

Well pilots have suffered broken bones before with ejection seats. It really depends on the altitude they eject from.

Hypothetical, yes, but the original question was more fun. People could have considered the actual technical part "can a plane be controlled after ejection / what damage does the plane go through during ejection" instead of being so uptight!

@Airsick  The original question was a highly tenuous hypothetical scenario where one pilot ejects while another, by some circumstance, is able to immediately re-enter the cockpit.

@J... The original question (and the edited version too) was about whether a cockpit becomes too damaged to be used after an ejection. In hindsight, it should have been "a mechanic triggers the ejection seat on the ground; could a pilot then enter it and fly the plane?" All the answers are about twin seats or gliding, and none are actually answering the "damage" part. I'm not sure what to do now.

@isanae So edit your question to clarify - as you've worded it here in comments this sounds like a clear and answerable question.

@J... I can't make an edit to my question that would invalidate all four answers. I'm thinking of rewording it to fit the answers better, and then making a new one.

If the airplane was controllable, the pilot never would've ejected in the first place.  Because the pilot ejected, it means that the aircraft was already hopelessly lost, so the idea of piloting it or landing it is moot.

@abelenky Really? I'm asking if a plane is broken after an ejection and your comment is that the only reason you'd eject was if it was already broken? I don't understand the utter confusion that stems from my question. If somebody knows how to fix it, go ahead, but even my curiosity has limits.

I believe that @abelenky point is that no pilot in his right mind would eject from an aircraft that he believes he could control enough to get it to the ground without killing himself. Therefore, the only reason to eject is if the plane is no longer flyable, i.e. "broken".  That said, I've tried adjusting the question to follow your "in hindsight" comment. If others feel their answers no longer apply, they can edit and/or delete. It might even get the question reopened.

I'm going to interpret safely as meaning successfully. Ejections mean safety has gone out the window - literally.
There was a case in the Vietnam War where a pilot continued to fly his heavily damaged F-4 after his RIO (back seat radar operator) ejected. He managed to keep it together long enough to get back over friendly territory before ejecting himself. Note, this was an interview I saw some years ago, I haven't been able to find a link to post.
In this case the airplane had been hit badly enough that landing was not going to happen, however if the RIO had ejected accidentally or the airplane less damaged then a safe landing would have been possible. So yes, flying has been done and landing is entirely possible after someone has ejected.

There is similar story recalled here which has a landing after RIO ejection.

The first test with ejection seats were performed in 1942 in Sweden with a Saab 17 and in Germany in 1941 with a Junkers 87 and in 1943 with a Heinkel 219 and Heinkel's pneumatic seat. Of course, then it was not the pilot who ejected but his back seater, but the aircraft did not need much modification for the tests. In each case, the pilot performed an uneventful landing after the test flight.

Saab 17 (above, source) and Heinkel 219 (below, source) during ejection seat trials.
To enable someone to fly the aircraft home after an ejection requires two conditions:

The second seat must be equipped with flight controls
The ejection sequencing is switched off, so the seats can be activated independently. Normally, triggering the sequence from either seat will eject all occupants.

It is exceedingly rare that both conditions are true in a modern combat aircraft. There have been a few cases where a crew member flew an aircraft to a successful landing after the pilot bailed out, but I know only a single case where the bail-out was done by ejection seat. It was a Boeing B-47, and the YouTube link is to a re-enactment of this B-47 flight in which one observer, who was also a trained pilot, took over after the crew had bailed out due to a fire in the electrical installation.
Read the last of the stories from this page for one accident in which everyone but the pilot ejected from an S-3 with a stuck nose wheel, and the pilot later performed a safe landing.
I guess you are concerned about the damage done by an ejection. The firing of the rockets happens in the rear part of the now very well ventilated cockpit and is a very brief event, so the flight controls and instrumentation should be in working order after an ejection. However, after the event nobody will be there to take over, and there is no way another crew member will be able to take over unless he/she has his/her own set of controls.
There have been cases of inadvertent ejection seat activations by mechanics on the ground. When this happens, a new ejection seat is needed, the shear pins and in most cases the canopy need replacement. After that, the cockpit area needs to be checked and cleared. But the airplane will return to service.
Fun fact: The XB-70 had ejection capsules to make ejection at supersonic speed possible and to protect the pilots in case of pressure loss. Life support systems and a minimum set of flight controls were duplicated inside the capsule, and the pilot could continue to fly the aircraft down to a safer altitude after initiating the encapsulation sequence. Only then he would trigger the ejection.

And it would be very difficult to fly with no seat!

"the flight controls and instrumentation should be in working order after an ejection". Can you confirm that the ejection is not actually damaging anything vital? If the ejection happened on the ground by mistake, could a pilot then enter the cockpit and fly the plane? Is there anything missing (attached to the seat maybe?) or broken that would prevent the plane from taking off? This is my actual question and I would accept this answer.

@isanae: Your question makes it sound as if you want to land after an ejection happened. Again, it is irrelevant whether all controls are still in place because nobody will be in the cockpit. If someone flies the plane home, he will sit in a different place with his own set of controls. If ejection happens on the ground, the plane needs several days of care before it can be declared flight ready. If somebody brings a chair and tries to fly without harness or canopy, he will be able to do so but needs to restrict his flight envelope severely.

"If somebody brings a chair and tries to fly without harness or canopy..." This is my question. I want to know the damage done to the cockpit. I understand that the plane would normally have to be repaired. I'm asking whether it's possible to put a chair in the cockpit and fly the thing.

@isanae: Normally no, no sane person would do this unless you point a gun to their head. In a desperate situation when this is the only way out, then yes.

@PeterKämpf in the movie Behind Enemy Lines it is portrayed that triggering the ejection mechanism starts destruction of various electronic systems. Does this have any relation to reality and could that also be used to destroy advanced avionics (to prevent them from falling into enemy hands)?

@transistor09: Yes, I know the movie. I have no knowledge, but think it to be likely. If you put some thermite next to the electronics, they would melt into a featureless blob. Flying around with some thermite in the cockpit, however, doesn't sound like a brilliant idea.

The fighter can remain airworthy (in the technical sense not in the regulatory sense) after ejecting.
For example the cornfield bomber made a belly landing onto a field after the pilot ejected.

Martin Baker uses (or used, it may have been retired) a modified Gloster Meteor to test ejection seats. The aircraft is piloted, with the seat being in a separate area behind the cockpit.
This aircraft is definitely reusable, it's been used to test ejection systems many times.

So yes, it is possible to design an aircraft in such a way that it can be flown after an ejection of (one of) its ejection seat.
Of course in case of operational ejections these are usually done after the aircraft has sustained enough damage that it can't be flown anyway, so having it flyable after ejection isn't a high priority. And without the crew on board it becomes even less of a priority, as the crew are the ones flying it in the first place.

After reading this reply, I checked the facts, and indeed, two out of the five remaining airworthy Meteors (WA638, WL419) are indeed (as of 2013) still used in "active service" that way, 70 years after introduction of the type. That's just amazing, and worth a tipping of the hat.

There was a case when Soviet MiG-23 was flying for more than 500 miles after ejection of pilot.
https://en.wikipedia.org/wiki/1989_Belgian_MiG-23_crash

Need to have more details in the answer, rather leaving link to reader.

@Lucky A MiG-23 got in trouble over Poland, pilot ejected. The aircraft flew on (presumably on automatic pilot) until the fuel ran out and it crashed in Belgium.

authors: B6007874กอบศิริ สีดาแก้ว


text:
How do pilots cope with pressurization changes?
I have tried

drinking a glass of water
yawning
plugging my nostrils and pushing air

but none of these seem to work - I still have a distinct pain in my upper sinus cavities when changing pressure in an airplane. I have the same pain underwater.
Do some pilots have this problem, and do they have a remedy?

If you haven't already, you should also try asking this in a diving forum. Equalizing is usually a much bigger issue for divers than pilots, so you're likely to get a good response there. This is a good place to start, DAN is a great resource for dive medical information and support. And see this question too.

(Amateur) advanced diver here.  You should consult a doctor.  Not being to equalise normally. for example with the Valsalva manoeuvre may indicate an underlying condition.

I know that I am more sensitive to pressure changes when I have a cold. A closed eustachian tube makes all the difference. What helps me most is moving my jawbone left and right - this opens up the tube and helps to equalize pressure.

Over time you just get used to it.  But you can do the valsalva trick and plug your nose and blow. Chewing gum and talking help too.

Me, I stay low.  Under 5000 AGL if I can help it, and I never, ever fly commercial anymore, those commercial jets yank the air pressure all over the place way too fast.

@Pondlife: Damn, we don't have a Diving Stack Exchange?

@Sean Well, sort of but not really :-)

There is a chance you suffer from aerosinusitis but you should consult a physician to obtain a proper diagnosis (Disclaimer: I am NOT a doctor). For what its worth commercial planes are pressurized generally to about the pressure you would see at 8000 ft. this equates to about .75 Atm. In the reverse case 33ft underwater already has you at 2 Atm.
When I fly (generally unpressurized) I usually chew gum which i find helps.

I do this also for high altitude climbing. I find it very useful at adjustments to pressure.


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Why is max power time limited for jet/piston engines?
Usually max power is time limited for jet/piston engines to 10 or 5 minutes. Can anybody explain the reason? What will happen if those limits are exceeded?

Maybe Nothing....
Maybe Catastrophic Failure...
Any number published by an engine maker (or any aviation part maker for that matter) is the numbers they have tested it to. Thus if Continental or GE claims a 2000 hour TBO but puts a 5 minute limit on max power, that in turn means that the 2000TBO number is based on operations within these published limitations. Exceeding these limitations may cause TBO to arrive sooner than expected and could possibly cause undesired operating characteristics. It is of course possible that if you drive the engine at max power for a time greater than suggested, it will throw itself to pieces. However, this is unlikely.
In some cases there are physical limits based on the materials used in the engine. If exceeding maximum run time provides a way to generate internal temperatures that exceed the limits of an internal part you could very well have an issue very quickly. From my experience with piston engines it's generally a wear and heat fatigue issue when flogging the engine at max power. That being said if the POH calls for a maximum of 5 minutes at full power and you spend 5 minutes and 30 seconds at full power on a climb out chances are you will be fine. If you do this routinely you may find that your engine hits TBO long before the published numbers.
This article also alludes to the fact that there may be other limiting factors such as the strength of the gear box the engine is connected to.

The shp of a turboprop engine is restricted by the strength of the gearbox that drives the propeller, and by the ability of the airplane to handle the thrust developed by the prop.

On any note I would think that most manufacturers publish numbers that are on the conservative side for many reasons.
Since this question is highly related to TBO number you should check out this article about some common myths around engine overhauling numbers and engine wear in general.
Definitions:
TBO: Time Between Overhaul. This is generally the lifetime of an engine. Although some people commonly think this is a legal number it is only manufacturer suggestion and you are free to exceed it (and plenty of people do).
POH: Pilots Operating Handbook. The document that outlines the limits and safe operation of a given airframe.

I suspect that somebody who needs to ask this question will also need to have abbreviations such as TBO and POH expanded for them.

I suspect that the answer might vary from aircraft to aircraft and engine to engine, so I'll answer specifically for an aircraft/engine combination I am familiar with.
The Lycoming O-360, of various models, was chosen by Robinson to power the R22 series.  This engine is widely used in fixed wing and rotaries, is more or less bullet proof when cared for properly and is serviced by a market with a good spares supply and availability of skilled mechanics and overhaul centres.
For the R22 Beta II, the engine is capable of producing 180 HP but Robinson said  we only need 130 HP, maybe 140 HP at most but can you make it lighter?  I forget the numbers - they came from an interview with  Frank Robinson, I'm sure Google will lead you to accurate ones.
Lycoming responded by making several changes without changing the major replaceable components including thinning the cylinder walls and making the cooling fins somewhat smaller.  This means that the engine is less capable of dispersing heat and consequently, cannot run at maximum power for long.
Eventually, they certified it at 145 HP (less than the maximum - i.e. "derated").  The POH (Pilots Operating Handbook) allows using the maximum derated power, 145 HP, for short periods, from memory, 5 minutes.  The engine life and reliability are only good if these limits are not exceeded.
There are also limits on how much power the drive train, including the gearbox, tail rotor drive shaft and tail rotor gearbox, can handle which place limits on the maximum power the engine can safely produce.
In an emergency, it is possible at sea level to exceed the 145 derated maximum since there is no physical device to stop you putting the collective into your armpit or opening the throttle wide but there is a good chance that doing so will damage the drive train or blades and if exceeded, a maintenance inspection is mandatory.  Using the whole 180 HP will lead to damage and has been implicated in accidents.

For gas turbine engines, the three measurements to watch are:
MTO: Maximum TakeOff thrust. (no more than 5 minutes)
MCT: Maximum Continuous Thrust. (okay, unless the turbine overspeeds or overheats)
MCL: Maximum CLimb thrust. (often the same as MCT)
Those three limits are the ones established by the engine manufacturer during extended lifecycle testing as sustainable while maintaining the engine's established time between overhaul. Exceed them, and the aircraft maintenance person must consider a shortened TBO if they don't want to risk an in flight failure.
And, yes, the manufacturer used up a pile of engines establishing those limits.
On piston engines, heat is the big enemy. Exceeding RPM isn't usually a concern, as most props become inefficient when the blades go supersonic, so overspeeding a piston engine is counterproductive. Overheated parts become weaker, and wear faster even if they don't break immediately. In particular the cylinder heads (and gaskets) will likely be the first to fail in an overheat situation.
Why is it possible to exceed those limits on aircraft engines? In his book Fate Is The Hunter, Ernest Gann describes it most eloquently, when talking about backfiring the engines on a DC2 to clear off ice that was closing the air intakes to the engines, causing them to lose power: This is terrible abuse of the engines, but not as bad as asking them to fly through a mountain. (anyone who holds a pilot's license should read that chapter on the icing incident... it's scary)
Unlimited overboost is there in case of dire emergency, when the choice may be either overhaul the engines prematurely, or crash the plane.


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Can commercial air traffic operate from uncontrolled airport, airspace?
Are there any airports with scheduled services where big jets (say 737 or A320) or wide bodies regularly operate without control tower?
Are there any rules (EASA FAA) for this?
If controllers go on strike can commercial air transport continue to operate?

What is the scope of your question @Andrius? So you mean US, Europe, or the whole world?

As Pondlife's answer mentioned, it's probably best to separate this question into a couple of questions. Operating from non-towered airports is fine. Operating the flight with no controllers at all (Tower, Approach, Center, or otherwise) is quite another matter, though. I'd be a bit surprised if they're allowed to fly unfiled VFR and they sure wouldn't want to remain below 18,000 ft for a flight of any significant length.

Related: http://aviation.stackexchange.com/questions/14016/when-is-a-control-tower-required

Is AFIS a control tower for you? Many commercial airports have AFIS instead of a TWR. And some have TWR in some hours and AFIS in other hours. And many very small airfield have a RADIO station. Is that a controller for you?

I will answer your question with what we can see in Brazilian Airspace and its rules.
In Brazil, there are some airports - non towered, operated by radio stations - which give information such as wind direction/intensity and temperature and QNH. Based on this information, the pilot decides on which runway they will land or take off, and relays this message to the radio operator. The operator will only relay these pieces of information to pilots monitoring the radio frequency.
Those airports are not controlled, then, if there is any strike, flying visually, no control will be effective.
For example, ARU/SBAU is a non towered airport, and TAM Airlines operates the A320F there.

The question specifically asks about commercial traffic and big (737/A320 and up) jets, yet your answer doesn't specifically indicate that these type of aircraft operate at the airfields you've described. In the US, there are hundreds of small, untowered GA airfields, but they don't see regular, scheduled service by larger pax aircraft like the 737/A320. If you simply left those details out of your answer, adding them in will make it much more complete, otherwise, it doesn't really seem to address the question.

Yes, I have answered according to the question. For example: ARU does not have a tower, and TAM Airlines operate there with A320F.

Fantastic, the addition of that last sentence makes this a great answer! Though, I don't think Brazil is part of EASA is it?  ;)

Brazil isn't part of EASA.

@FreeMan FAA only covers USA homeland. Only european countries are part of EASA. Brazil is in South America so it would obviously be outside the jurisdiction of both organizations.

Sorry, guys, I'm kinda old school. When I grew up, a smilie indicated sarcasm. I'm fully aware that Brazil isn't anywhere near Europe. (At least, in a regulatory sense - with these wonderful flying contraptions, it's less than a day's travel away, and that's not far at all!)

In Finland, which is an EASA member, we have AFIS airports, where carriers operate regularly. AFIS is not an air traffic control, but offers information service. Airspace classification is G+.

The Canadian Arctic has B737 scheduled airline operations to many uncontrolled airports that have no control tower.

Totally OT, but that first route map has me wondering what languages are those in the top left corner? I'd assume the bottom two rows are some sort of Indian/Eskimo dialect, but the middle row looks like some MathJax or APL code.

I am quite sure that those are 3 different Inuit languages.  Here are some of the languages that are used in Canada's north: Tlicho, Inuktitut, Inuvialuktun,  Inuinnaqtun, Chipewyan, Slavey, Gwich'in, and Cree.

Also OT: in the second map, who had the bright idea to color the land blue and the water white?  That took me a long time to realize what I was looking at and invert my sense.

@FreeMan: The script is Canadian aboriginal syllabics. The language is probably Inuktitut, which is an official langauge in the territory of Nunavut.

Wow, that's cool, @HenningMakholm! Thanks for finding that and sharing. Also, my apologies for showing my US-centricness in assuming "Indian/Eskimo" and forgetting that our Canadian friends are the Inuit. /OT wanderings. We now return you to your regularly scheduled SE forum operations.

American Airlines operates an A319 seasonally from DFW to Gunnison (KGUC), which is an uncontrolled airport. There are probably many other similar examples.
An airline flight arriving at an uncontrolled field operates just like any other aircraft: it will almost certainly be IFR and fly an instrument approach, or a visual approach if conditions allow it. Radio calls, pattern etc. should be the same as for any other aircraft arriving IFR at an uncontrolled airport.
The airline's OpSpec might have some specific procedures for uncontrolled airports, but otherwise it's just another aircraft.
Controllers going on strike is a totally different scenario; you might want to ask about that separately.

Any plane can land at any airport as long as the runway is long enough. There is no regulation saying that a 737 cannot land at a non-controlled airport. All of the commercial pilots that have had their training in the private sector have had to land at non controlled airports. I say all, but I'm sure there are some exceptions. Let's just say most. It is no big deal.
Here at our local airport, KLBX, there is no tower and there are four large jets that come and go every single day, even when the weather is IFR.
There is so little realistic understanding of aircraft and air travel due to the continued misrepresentation by the media and movies.  There was the incident of the control tower guy falling asleep and the commercial flight had to land without the tower control. It was all over the news as though it was a miracle that the plane didn't just crash all over the place. As though a pilot cannot land a plane without the tower saying "Cleared to land 13R." That's all they do anyway. The pilot is still responsible for looking and seeing if the runway is really clear and ready to take the plane.
In IFR conditions there is still what's called the minimums. If you can't see the runway when you reach the minimums you are not allowed to land there. Again, there is an exception, but it won't be available at non-controlled airports because of the cost.
I don't know about Brazil or Japan or any other country. I fly in the US only, and most of it in Texas. You'd be surprised how many non-towered airports there are where you even have to turn on the runway lights from your plane at night.

Thanks for that - say, how do you turn on those lights?  You mean radio a human and ask, or is there "an app for that" these days??

@JoeBlow - No controller necessary - see: https://en.wikipedia.org/wiki/Pilot-controlled_lighting

got it !  click five times eh.  :)  never heard of it, thanks for that

How do you ensure separation while positioning for the approach in the clouds and IMC conditions?

@Andrius Usually one-at-a-time traffic. Approach control clears one aircraft for the approach, terminates radar services, and waits for them to report that they're on the ground. Nobody else gets an IFR clearance in the meantime. This would break down quickly if there was a lot of traffic, but if there were a lot of traffic, the airport wouldn't be uncontrolled.

@JoeBlow It's called click-and-pray. Just be aware, depending on the equipment installed at any individual airport, the number of clicks may differ, and there may be a different number of clicks required for low, medium and high intensity runway lights.

@DavidC.Rankin - lol, I can only imagine

Runway length is not the only criteria.  The weight bearing capacity of the runway is  a factor.  Also in northern Canada, many fields are gravel, and commercial flights operating there (eg B737-200) are equipped with a gravel mod, which suppresses the gravel pattern from the nosewheel, and also uses bleed air to suppress the pre-inlet vortex which can introduce stones into the inlet.

Usually any airport with enough traffic that it would attract a big commercial jet will merit a tower. However, there are a few weird exceptions here and there and some of the other answers have described these.
I think you may be thinking that a tower would be necessary somehow or that flying a heavy into an airport without a tower would be dangerous, and that is not necessarily true.
Pilots can self-organize and land themselves just fine without a tower. The tower is mostly there to speed things up and enable large volumes of aircraft to land as quickly as possible. If an airfield is busy and there is no tower, then the aircraft will tend to spread themselves out more, approach from longer distances and do things more slowly. With the tower there it speeds everything up.
If an airport is out in the middle of nowhere and does not get any traffic, then there is no need for a tower and it does not really matter whether the plane is big or small.

authors: Vladimir F Героям слава


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Why is the angle of the horizontal stabilizer marked on the fuselage?
Why are the angles displayed on the fuselage?
I understand having markings with depth on the hull of boats, but I don't understand the use case on a plane.

Photo of the root of the trimmable horizontal stabilizer on an Embraer ERJ-170 (wikimedia.org).

To ease some step in the maintenance procedures? Also, this is not al all universal, quite a few aircraft do not have such detailed markings.

That looks like a 737 and you usually only see markings at neutral, full up and full down.  That's probably a customer request to allow for checking it during walkaround.  It made me think there might be an MEL that allows dispatch with an inoperative trim indication, requiring the crew to check the position outside before departing, but that seems kind of far fetched.

I don't know from what airline the picture comes, but I've seen some of Ryanair's planes having similar markings, but just the the 3 notches

Now I wonder if those marking are also present on aircraft without THS.

I believe it is to ensure proper alignment during installation.  I have seen attachment shafts that are splined, and when sliding the control surface onto this shaft you would want to ensure that the leading edge mark is properly aligned with the fuselage mark appropriate to the trim setting.

I suppose you're referring to re-installation after a maintenance of some sort. If it were the initial installation in the factory, the body would most likely still be unpainted and there's probably a jig for that.

Yes, good point...

I don't have the reference but it's showing the trim setting.  The picture looks like is an Embraer 170 on which the entire horizontal stabilizer moves.  The gauge gives a quick visual setting to confirm the the trim set in the cockpit matches the actual trim.

The markers are for the ground crew member to report to the flight crew the actual position of the stabilizer trim, which the flight crew checks against the cockpit reading. This is just to ensure that the stab trim sensors are functioning properly. It is part of the launch checklist, usually. (the photo above shows 4° nose up trim.)


text:
What are capabilities of small Airplane in general?
In general what can i expect of small, 4-seat, light airplane? I am specifically interested in the Pipistrel Panthera, though general responses would be appreciated.

What is usual range of that kind of plane?
What is the worst weather under which it can fly?
How expensive is to fly internationally with that kind of plane?
What is the procedure and usual cost for example if I fly from Rome to Prague, what border control checks can I expect? How and what kind of taxes related to that particular flight would I pay?
If a plane is declared to have range of 1900 km, what is practical range in practice?
If regular service for an airplane is declared to be after 7000 km of flight or X hours of flight, what has to be done usually in those services? Changing of oil, changing of filters?? How expensive usually is that?
Anything else you think is important to know about possessing and airplane of that type?

This is a lot of questions asked in one. Please try to narrow your question to a single core question, perhaps on range?

Hello mariotanenbaum, welcome to Aviation.SE. These are too many questions at once to be answered. Please try to cut it up to multiple, single-issue questions.

And this question may help you as well.

I know that it's many questions, but imagine you are somebody who doesn't have any info and you don't want to spend 5 hours searching for each answer. Also, i didn't ask for great details, just in general. Doesn't need to be very precise and 100% correct.

@mariotanenbaum Without splitting the question up, the answers must be kept short and specific, which is less useful to others looking for information. The title of "what are capabilities" is also very vague and unhelpful for anyone else looking for the information. If you limit the questions to just the aircraft you mentioned, it would be more useful.

@fooot feel free to custom title as you wish.

Are there border control checks between Rome and Prague? Aren't both of them in Schengen?

@cpast Ok, but does that mean that somebody with a plane can just fly around? How are the flighty announced? What about Belgrade to Ljubljana procedure? etc..?

You have a few questions and the answers to them vary greatly based on the plane in question. It's often said you should chose the plane for your "mission" which means you should think about what you would like to do with the plane and then chose the plane that best fits that "mission". But anyway let's address some of the questions at hand.

What is usual range of that kind of planes

This depends on the plane. Small planes can get anywhere from 500 nautical miles to upwards of 1500 nautical miles depending on fuel load and optional tank configuration. But the middle of that range seems to be the average. I have found that range is more dependent on how long you can sit in the plane not now much gas you can carry. Remember there is no bathroom on these little planes and some are not the most comfortable things in the world.

What is the worst weather under which it's ok to fly that kind of
  airplane?

Although this is changing most small aircraft are not certified to fly in ice. Some can be modified to do so and some come with the option when you buy it. That being said I don't know if I would fly a small plane in ice but IMC is possible and done all the time. Remember also that fancy equipment does not always mean you are safer, you are still flying a tiny plane in bad weather.
Rain is possible but keep in mind rain on the ground could mean ice in the air depending on the temperature. Some small airplanes will be able to climb above this but that depends on plane.
Wind is limited by the airports you are flying to and from. If the wind is blowing down the runway you are good to go but every small plane has a maximum demonstrated crosswind component that will limit your ability to fly in high winds at some single runway airports where a crosswind landing is the only option.

How expensive is to fly internationally with that kind of plane.

Again this changes from plane to plane and country to country. Small pipers can be flown for (from what I have read) under 10K(USD) a year and less if you don't fly very often. With older planes you will pay more in maintenance and less in up front cost while with a new plane you will pay more to buy it and less to maintain it as its fresh. You will also have to factor in gas and insurance. Insurance depends on YOU and your flying time so its hard to say what that will fall in. Gas here in the US (100LL) is around 4.56-6.00 where I am so figure in that based on fuel burn etc.

What is the procedure and usual cost for example if I fly from Rome to Prague, how the border control checks me, how and what kind of taxes related to that particular flight do I pay. Please, don't miss anything.

I don't fly in the EU so I will refrain from commenting here.

If a plane is declared to have range of 1900 km, what is practical
  range in practice?

Here in the US you are required to flight plan with enough fuel for your flight plus 30 minutes of reserve. I don't like when companies put range because this is very much based on the winds and your course. If you get a 40 knot tail wind you will very quickly increase your range, while a 40 knot headwind will bring the number back equally as much. I would calculate range based on usable fuel and fuel burn of the engine. but if they are saying 1900KM I would plan for the 1750KM range to be safe.

If regular service for an airplane is declared to be after 7000 km of flight or X hours of flight, what has to be done usually in those services? Changing of oil, changing of filters?? How expensive usually is that?

Aircraft service is (as far as I know) done on hours not miles flown (although they are related in a way. Here in the US you need a yearly inspection which includes lots of things like testing gear and other components and ever XXXX hours when your engine hits TBO (to be overhauled) you need to overhaul it. This overhall can be costly but is very dependent on the engine. It can range anywhere from 15K to (insert large number here). You are also responsible to have anything fixed should it break obviously.

Cost to park

There are 2 things here your storage cost and the cost when you actually go somewhere. I fly out of KPNE and have spoken to a few people about the cost of a tie down/hangar. It seems I can keep an airplane in a tie down for less than $100 a month but it would be outside all the time. Hangars get pricy and can be rented or bought. There are lots of small airfields where I am and I'm sure its possible to store a plane for cheaper than at KPNE.
As for going somewhere that depends on ramp fees. Here in the US these fees are sometimes waived if you buy gas or very nominal in the first place. Some airports also have a small landing fee (KPNE is $5). I don't know about EU (although I'm sure they have it) but here in the US you can get the AFD (airport facilities directory) which has lots of info on these kinds of things. Most airports/FOB's now have websites that list their prices as well.

Anything else you think is important to know about possessing and airplane of that type.

It seems you are looking for a fixed number to a question that does not have an answer like that. You must first identify your mission then you can find a plane to fit the mission profile. You can then look at the prices of other people who have owned that plane and you may find what you seek but you will also find that there is a HUGE deviation in the prices as no two planes are alike.

Almost an answer i was looking for. I know that it's not possible to present fixed prices. Not even possible for a car. However, if somebody could clarify more about: "bad weather", how strong winds, rain, storms? (anything to compare to?) And of course, flying internationally, how much does it cost to land somewhere "from-to"? And how much it can cost to park an airplane in bigger airport? Does this small airplanes fly over ocean or it's a no no due to something?

I will edit my answer to reflect some of these points.

great, thank you very much, i just hope somebody from Europe will add some info for EU about airport lending practice etc...

Weather capability is much more likely to be limited by your ability rather than the plane.  To fly in anything but clear weather (VFR), you will have to get an instrument rating, and stay current.  This has considerable cost, both in money and time.

Jamesqf is 100% correct on this one, I was more addressing some of the physical limits of the aircraft.

You must also factor in the load carrying capacity of the plane, and your intended load.  It is rare to find a small plane that can fill to capacity both the seats and the fuel tanks, and if you must carry a heavy passenger and baggage load you must leave with less than full fuel...  i.e., less range with full passenger/baggage load.


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What are the costs and labour hours for converting a B767 airliner to an aerial refueling aircraft?
To win the tender of RAF Future Strategic Tanker Aircraft, Boeing, BAE systems and British Airways formed Tanker Transport Services Consortium to offer air-to-air refuelling to military jets, using converted aircraft based on the B767 passenger jet. BA would provide the aircraft, Boeing would provide the conversion technology, and BAE systems would perform the majority of the aircraft modifications.
Roughly speaking, how much does it cost and how much labour hour is needed to convert a B767 airliner to military aerial refueling and strategic transport aircraft?

As this a miltary-related related operation, it may be classified.

@ManuH I don't see why anything asked in this question would be classified. Budgets are usually a matter of public record and the time it would take to convert a plane is something that an enemy could probably guess sufficiently accurately that there'd be no point in classifying it. (OK, "no point in classifying it" doesn't mean "it's not classified" but...)

It seems to cost a lot. E.g. PLA AF uses IL76 and modified it into KJ2000, but still bought IL78 instead of building one from stock IL76.

It's very difficult to answer this question directly, mostly because that the costs you or I would face when undertaking such an endeavour are primarily capital in nature. For a large airline (or other organisation), they'd have staff and equipment on hand already, and the price an organisation like BA or BAE pay for parts is almost certainly different to the list price.
That being said, the deal in question is notoriously bad value for money. From that source, the taxpayer will be paying around £10.5 billion for 14 Airbus A330 troop transport/tanker jets with a capital value of only about £1 billion, although the deal also includes maintenance. Although converted to military specification, the converted passenger jets will not be flying into a war zone any time soon.
Interestingly, it appears that the government itself didn't really know the answer to 'how much will this cost', even as they were signing the contract to provide new aircraft. Specifically, a critical report from the National Audit Office concluded that there was 'poor access to full cost data – the Department never gained visibility of detailed sub-contractor costs and margins for the aircraft and their modification'.
In other words, nobody knows!


text:
How many staff are needed to support aviation on an aircraft carrier?
An aircraft carrier is the largest type of warship and is used to transport, operate, and maintain military aircraft.
The staff which support aircraft in the carrier can be divided into 2 groups.
Some "variable" staff are directly related to the aircraft operation like Pilots, the number of those staff is proportion to the number of aircraft.
On the other hand the number of the "fixed" staff is fixed, regardless the number of aircraft, like Air Traffic Control.
How many of the 2 different types of staffs are employed? To simplify the answer, please use the biggest Nimitz-class as example.

Where do you draw the line between supporting aviation and not? Are the sailors who take care of moving and loading munitions for the aircraft supporting aviation? An aircraft carrier will have a number of cooks, for instance. Are those cooks supporting aviation when they feed the pilots, fuelers, etc...? Is the helmsman supporting aviation when he turns the carrier to align with the wind so aircraft can land? What about the reactor mechanic who keeps the lights on?

The purpose of an aircraft carrier is to extend air power.  Anybody onboard an aicraft carrier who does not support that purpose is not needed, and therefore does not exist.

I don't think taking the biggest aircraft carrier as an example is relevant. If you take the aircraft carrier with the minimum crew (surely it is not the biggest one), you'll result in the minimum staff needed to support military aircraft operations while in the middle of the ocean. I think it is mre relevant to compare several aircraft carrier taken into account the number of aircraft supported.


text:
Why does XKCD say that autogyros will crash if the pilot reacts to a stall as in a normal airplane?
This recent XKCD comic is all about autogyros.

Image is copyright XKCD, licensed under CC 2.5 BY-NC
The note at the bottom is what got my attention

Extremely safe, unless you do the one thing you instinctively do to escape a stall in a normal airplane, in which case it will crash immediately

So what is that one thing, and why does it not work in autogyros?

Odd when the line above says "never stalls"....

@Trevor_G: The text doesn't say it will stall, it says it will crash. Entirely different.

@Moo, it says it will crash if you do the natural thing to escape a stall. Trevor's point is that if it never stalls, there would be no reason to do that thing.

It's the one thing you do [to escape a stall in an airplane], not to escape a stall in a gyrocopter, referring to the action you take in airplanes to escape a stall. It's not implying you do it to escape a stall in the gyrocopter.

See also https://aviation.stackexchange.com/questions/49894/auto-gryos-is-xkcd-on-the-ball

how isn't this a dupe of https://aviation.stackexchange.com/questions/49894/is-this-xkcd-comic-list-about-autogyro-features-accurate?rq=1?

@cat Different questions, same subject material. And my question was first

If you had read teh comments thread at  forums.xkcd (or echochamber.me), you'd have the answer already.

Machavity, you rejected both of my edits (1, 2). Don’t you agree that quote markup should be used when including someone else’s content?

@Machavity: Alright, I suggested another edit. In case there’s a misunderstanding: I’m not talking about the mouseover text, but about quoting the comic (with >), just like you quoted the sentence taken from that comic (as far as I can see, no accepted edit added the quote markup for the comic yet). The quote markup makes clear that it’s not part of the user-generated content, which automatically gets licensed under CC BY-SA 3.0 on Stack Exchange sites (the comic cannot be licensed/used under this license).

@unor Misunderstood. I thought it was the alt text stuff. It's redundant to quote it because 1. I link to the source 2. I mention the source in the title. The image is implicitly not mine, and I can't think of anywhere in the SO/SE network where making the image a quote is used (beyond spoiler tags). See this Meta.SE for more info

@Machavity: The Meta discussion is not about the licensing issue (but possibly the other way around: using quote markup to get a visual effect even if the image is not quoted). -- Linking to the source doesn’t make quote markup redundant; in fact, both should always be done (link and quote markup).

@unor Fair enough. As Meta.SE has no guidance I've asked it directly. Feel free to chime in

@unor Per Meta, I've rejected the quote edit and added a proper CC 2.5 BY-SA link. I think that should suffice

Pretty difficult to answer this one with the obligatory XKCD!

They're a whole lot closer to a helicopter than an airplane IMO. What happens if you react to it as if you've stalled a helicopter? Is step one of autogyroing a helicopter : pushing on the stick?

It's not a helicopter at all, nor an airplane. The thing you're most familiar with that It's aerodynamic characteristics match is a kite, especially if you built one out of a maple seed.

That one thing is to unload the rotor too much (i.e. "push on the stick"):
From explainxkcd:

... Unfortunately, as soon as the rotor stops spinning, the whole aircraft falls like a brick and the rotor may be impossible to restart in flight. This is a situation that should be avoided at all costs.
Normally it is not a problem since the weight of the aircraft keeps the rotor spinning. However, if the weight becomes too low or even negative, the angle of attack will become negative, and the rotor will slow down and eventually stop. It can happen when the pilot "pushes on the stick" and dives.
Unfortunately, "pushing on the stick" is also how you escape a stall in a fixed wing (normal) airplane as it is a way to regain airspeed. This is actually a counter-intuitive maneuver but because a stall is an emergency, pilots are trained to do it instinctively. It can trick a pilot trained in fixed wing aircraft into doing the one thing that shouldn't be done on a gyro.

@Wayne Conrad  I use to fly autogyros, and I believe that your answer is OK. An autogyro should always have the rotor duly loaded, and zero or negative Gs must be avoided at all costs. Concerning 'stall recovery for an autogyro', if –for whatever reason– the rotor blades slow down so much that they stall, you'll crash...

So what is the correct action in the event of a stall?

The comic also claims they "never stall", so would you just be reacting to buffeting or what that feels like a stall?

@GrimmTheOpiner That's what I hoped someone who actually knows something would put in their answer.

@NickT  I'm pretty sure that's the implication.  Sort of like "I thought I was going to be late so I ran like crazy only to find out I was early"

Could it be that autogyros are actually bad at descending then? Try to lose height too fast and ... you'll suddenly start losing height waaaaaay too fast....

Why is it counter-intuitive to push the stick forward when stalling a normal airplane? Wouldn't the instinctive response to stalling and losing speed be to push forward to dive? (I'm not a pilot!)

@ChristopherShroba It's an unfortunate wording in the quote.  Pushing forward isn't intuitive for any type of aircraft--it's taught.  But what they mean is that pushing forward to lower alpha is the "intuitive" (that is, conditioned) maneuver in an airplane.  It's the wrong maneuver for an autogyro.  So, because the "intuitive" maneuver (for an airplane pilot) is wrong in an auto-gyro, then it's "counter-intuitive."

This is a well known problem with gyrocopters. The first answer was partially correct in that the problem was caused by pushing the stick forward and unloading the rotor. However, the problem wasn't a slowing down of the blade. The actual problem was that many of these gyrocopters would tumble under these conditions. If you were close to the ground you would crash before you could recover. And, even if you had altitude the tumble could overstress the rotor and a crash would still occur. The biggest problem though was that no one seemed to know why and since those who did tumble didn't usually survive there wasn't anyone to ask. So, if you flew a gyrocopter the first rule was to never push forward sharply and unload the blade.
Eventually, people who understood aerodynamics and physics got involved. They studied gyrocopters and realized that it wasn't a problem that was inherent to the type. The actual problem was that many of these had a thrust line that was above the center of gravity. In the small gyros the pilot's weight accounted for a lot of the loaded weight and the pusher configuration meant that the pilot's seat blocked the airstream. So, there was a incentive to raise the engine both to get clearance for a larger propeller and to get the blade up into clean air.
The A-10 Thunderbolt II has a similar problem. The engines are placed above the fuselage so that the hot exhaust goes over the horizontal stabilizer where it is blocked from view of heat-seeking missiles on the ground. This high thrust causes the A-10 to pitch downward. The solution was to angle the engines downward slightly which would normally make the plane pitch up. So, these cancel out.
So, anyway, the high thrust line isn't usually a problem on gyros since the main drag is from the rotor which is even higher. However, this doesn't work when you unload the rotor. Unloaded, the rotor drag goes to zero and free-body physics takes over. If the thrust line is above the CG then the aircraft will rotate forward and if it rotates far enough you will tumble. The only solution is to lower the thrust line so that it passes through the CG. This can make the aircraft pitch up more since the drag from the rotor is still high. You can try to counter this by angling the thrust line up but this may put it back above the CG. And, the thrust line might still be above the CG if another lighter weight pilot flies.

Why would a gyrocopter have so much forward stick travel in the first place that using it will make it crash?

Imagine what would happen if you were driving at normal highway speed and turned the wheel sharply all the way to the stop. Controls have to deal with the worst case such as maneuvering in a parking lot or pitching up during a landing flare. This does not mean that full or rapid control movement is safe or advisable at high speed.

I believe what the comic is referencing is Mast Bumping. Rotor blades are very flexible, and for a bunch of reasons, are free to pivot around the mast.(The shaft the blades are spinning around) In normal flight, the blades are held taut by centrifugal forces and the weight of the rotor craft they are supporting. If a pilot were to suddenly push down on the Cyclic, you can create a low G, Zero G, or even a negative G situation. The blades are not having to support the weight of the aircraft anymore and the blades can potentially pivot so much as to strike the mast, tail, and even the fuselage.
So if an Autogyro pilot got into into a high angle of attack situation, and reacted by suddenly pushing the nose down into a zero G situation, the rotor blades would float weightlessly along with the aircraft. Its usually the next action that causes mast bumping. The pilot, out of his high AoA predicament, now pulls up to level off. The blades, still weightless, pivot without any resistance and strike the aircraft. This is rarely a survivable situation.

Doesn't mast bumping more specifically refer to the rotor head tilting to the point where it strikes the side of the rotor mast and fractures it?  Maybe it includes the strikes to the of the aircraft as well, but I thought it was more specific.

@EricHauenstein is correct (hence the term mast bumping.) Parts other than the mast can break in the course of the mishap, but you've got the basic process right. Additionally: this is predominantly an issue with teetering (e.g. 2-blade) rotors (which are common to most autogyro designs as they are the simplest to make.)


text:
Why do aircraft piston engines consume so much oil?
This question is related to single/twin piston engine aircraft. After flying in a Cessna 152 and a Piper Dakota I have noticed that they both consume a lot of oil. Oil check is an integral part of the checklist. Pilots carry extra bottles of oil in the back. Why is this so? Especially compared to car engines that are 'similar' and do not require such regular top offs?

how often do you run your car engine at full throttle and for how long?

And those are inline engines, there's a saying about radials, that if it's not leaking oil, something must be wrong.

@user3528438 how often do they fill up oil in car racing?

I am an A&P and thought the same thing before getting my university degree. High oil consumption is a sign of an overly worn out engine or neglected engine. If an engine has excess oil consumption something is wrong and it is unsafe - period. There are also quirks such as the Lycoming 0-360 used in the C-172 will blow out any oil above 6 or 7qt even though the mfg recommends 8qt - pilots learn not to put 8qt in. Jet engines have increased oil consumption as they wear and that is one criteria used for overhaul for them too. An aircraft engine should burn no more oil than a well maintained car.

@jwzumwalt That's very good information. You should add that as an answer.

@user3528438: That's actually not so relevant. As a designer, you optimize for the typical case. So a car might have excessive oil leakage when running at max RPM, and an aircraft when running at low RPM, but neither should consume much oil in the opposite case.

"Oil check is an integral part of the checklist." That, of course, being in part because having too little oil in the engine at 8,000 ft AGL and quite possibly miles from the nearest suitable landing site, let alone the nearest airport, can be a little unsettling to the pilot and any passengers. It's a fairly quick check on the ground that can save you plenty of headache during the flight; the same can be said for quite a fraction of the checklist items in that class of aircraft, especially those in the preflight check checklist.

@jwzumwalt: The question, though, is what constitutes excess consumption?  My Insight & Miata (both with over 200K miles) don't consume a noticable amount between oil changes - a period about equivalent to 100 hours on an aircraft engine.  My '80s pickup will leak about a quart in the same time.  '60s cars I've driven might use a quart in 1000 miles.

@ jamesqf "The question, though, is what constitutes excess consumption?" Where did you read this? 100hrs=200k? Redo your calcs. 2000hrs is roughly equivalent to 50,000-75,000 miles.(30-35mph * 2000hrs = 70,000mi)

@jwzumwalt: I think you misread what I wrote.  I meant that the oil change interval - 7500 miles - is about equivalent running time to 100 hours (figuring mostly highway driving, of course).  I do change the oil &c at recommended intervals.  I mentioned 200K miles, parenthetically, to show that they're not new cars: they have a reasonable amount of wear on them.  So for a typical aircraft engine - say an O-360 - what's expected oil consumption, and what's excessive?  A quart in 10-20 hours?

@ jamesqf: Mfg do not specify, but the University of Iowa used 12 planes to established the average oil consumption at TBO (1500/2000hr) was 1qt per 13hrs. For a car, that's about 1 qt per 450mi which for anybody that has the misfortune of owning a clunker is in pretty bad shape. Which makes sense because most people accept a rule of thumb that a car is on its last leg when it uses 1qt@500mi. This happens to correlate with my Mitsubishi SUV at it's present 140k mi.

@PlasmaHH in the more serious car racing leagues, engines are completely rebuilt (which involves draining the oil and replacing with new) after every 1-2 races. Generally no more than 24 hours of runtime between, and more often only a couple hours. In top fuel drag racing, the engine is rebuilt after every 3-5 second run.

@Davidw As far as I can see, most GA planes (and, in particular, the ones mentioned in the question) don't have radial engines. I think radials were mostly used on larger aircraft: even things like the Spitfire and P51 Mustang were using V-12s

@DavidRicherby Which I did not suggest was the case. Also, a majority of US Navy fighter aircraft up until the jet age were equipped with radials, including the relatively small F3F and F4F.

Automobile engines are not similar. They are liquid-cooled and therefore can be built to much tighter tolerances with regard to thermal expansion and contraction.
Air-cooled aircraft engines must deal with a large range of operating temperatures and oil is consumed due to the relatively looser fit of the piston rings.

Thanks. I assume you are saying that because the piston rings are looser fit the gap must be filled by oil. Part of this oil gets burned during the normal internal combustion cycle. Hence the increased oil consumption. The lose fit is needed because of higher operating temperature range of the air cooled engine compared to the liquid cooled engine. This makes sense.

Aircraft engines also are basically 1950s (if not earlier) designs.  Many still flying were built in the '60s & '70s.  Most 1960s car engines leaked & burned oil - after a few years, it was common to need a quart every few thousand miles.  The oil used was commonly 30 weight or thicker.  Modern car engines, like the one in my Honda Insight, are built to tighter tolerances (made feasible by modern tooling) and  run a much thinner 0w20 oil.  After 200Kmiles, mine still doesn't leak or burn a measurable amount.

@jamesqf : this begs the question why there weren't any significant improvements in aircraft piston engines during the last 50-60 years, in contrast to cars.

@vsz I guess other problems took priority. Engines and airplanes have definitely been improved much over the years, but you can't solve everything at once. I'm wondering about actual numbers though, to put all myths to bed. Feel free to make a new question.

@vsz: Three reasons that I can see. First, if I'm not mistaken, the majority of GA aircraft and their engines were actually BUILT in the 1950s through mid-70s.  (Compare the price of a '60s Cherokee, say, against a new Warrior.)  Second, simple economics: the cost of R&D & tooling for auto engines can be amortized over millions of units, vs thousands for aircraft engine.  And finally, automotive emission controls and fuel economy standards forced the automakers to improve, while FAA regulations discouraged innovation.

@jamesqf : so, it's basically because there is not enough demand for new GA aircraft, as there are enough old ones to saturate the market? Makes sense, as hull losses are rare enough, and existing aircraft are maintained regularly with new parts. The club I was flying at, had both gliders and tow-planes built in the 1960's, and parts are still manufactured to keep them airworthy. It seems most GA aircraft are like Theseus's ship today.

@vsz: I wouldn't say that it's lack of demand, really.  It's really lack of supply: there aren't that many people who're able (or able but willing) to spend upwards of a quarter of a million US dollars on a new plane: http://www.planeandpilotmag.com/article/single-engine-piston-planes/  Especially when the 1960s equivalent to that plane can be had for 10% of the price.

I guess this answer forgot about the VW and Corvair. They did not have any more oil consumption than any other automobile when maintained correctly.

@jwzumwalt: Not my experience.  While I've never owned a VW or Corvair, it was quite usual for cars of that era to consume oil.

Prior to 1979 when Chrysler/Lee Iacocca made computer balancing an industry standard, the average car lasted about 50k on dirt roads and 75k on highways. They came apart from vibration not design. After 1979 and computer balancing, autos immediately began to last 150-200k miles. Aircraft engines are still not normally computer balanced.

This begs the question: why aren't aircraft engines liquid cooled?

@JakeRobb weight and complexity

As I think most folks here tend to be A&P's I'll add this. Aircraft horizontally opposed four cylinder engines also use specifically "asheless dispersant" oil because the oil is pumped to lubricate the top of the cylinder and a decent bit is burned in combustion. So yes, there is a line that can be considered "excessive" and that has a lot to do with wisdom in a small piston engine as opposed, to a jet where there is generally a one pint per hour limit, or something to that affect, where anything more than than that would require an oil consumption run. But as far as aircraft piston engines go, they do burn oil because they lubricate differently than an automobile engine.
Cheers !

'Air cooled engines' is a popular misnomer... oil does the primary cooling, with the fins on the cylinders only dispersing part of the heat. The oil, in addition to lubricating, draws heat away from high temperature points, like the cylinder heads, bearing surfaces on the crankshaft, and to a degree, the cylinder walls when oil splashes on them.
For a variety of reasons, oil/air cooled engines tend to consume more oil than water cooled engines, from the wider temperature range the engines experience, to the oil doing double duty.
In addition, the flat cylinder layout can result in some oil loss on startup, from oil pooling in the cylinders when not running, which doesn't happen in vertical or V cylinder arrangements that are typically used in automobiles. This is especially true of radial engines, which have some cylinders inverted, letting oil pool on the pistons when not running, leaking past and getting into the combustion chambers. That's why radial engines tend to expel huge clouds of smoke when started, as that oil burns off.
This is also true of automotive oil/air cooled engines, such as the flat four used in Volkswagen vehicles of the 1950's - 1980's, and the flat six in Porsche 911's until the wide temperature range of such engines ran up against tighter emissions controls. Those engines were also noted for their higher oil consumption.


text:
Does RPM refer to the speed of the engine or the speed of the propeller?
I followed discussion here: In a constant speed propeller, why does the RPM drop with a prop pitch increase?, I got confused about the RPM there. As the opening statement said in that discussion, "When a constant speed propeller changes its pitch from low to high, RPM would decrease."
From that discussion said that the RPM there is not the RPM of the engine that used to power the airplane, but the RPM of the propeller itself, how fast it rotating after the pitch was changed. The more pitch of course will produce more drag and as the product, the propeller will rotate slower than previously.
Please you masters of the aviation, please confirm if it is true, the RPM is the rotation of the propeller itself and not the RPM of the engine/turbine used to power of the airplane. That have confused me for quite long time and made me very difficult to understand many explanation.

Propeller RPM will always be the same as engine RPM unless there’s a gearbox between the two - or in a shaft failure case of course. Not sure I understand your question correctly...?

I mean, the RPM forcibly reduced by the induced drag rather than the RPM decreased by the pilot?

Yes it is the propeller RPM.  If the engine is direct drive, the engine and propeller RPM are the same.  If the engine has a propeller reduction gearbox, then engine RPM and propeller RPM are different, the propeller RPM being the engine RPM minus the gear reduction.
Propeller RPM is controlled by a flyweight governor, like those spinning ball speed regulators you see on old steam engines.  The flyweights control the oil flow to the prop to vary the pitch. The prop control lever applies a spring preload to the governor flyweights and the amount of preload determines at what RPM there is a state of hydraulic equilibrium so there is no pitch change happening. The speed of the governor is a function of the speed of the propeller in either a direct drive or geared engine.

I think you mean "propeller RPM being the engine RPM divided by the gear reduction."

Yeah close enough lol.

So @John-K, can I say that the propeller's RPM decrease is due to the load that affecting (decreasing) the engine's RPM? Just like a truck's wheel that slowing (decreasing RPM) due to its load or due to the climbing road that finally will decrease the engine RPM? Is that my analogy acceptable?

My concern here is to avoid my misunderstanding that the propeller's RPM decreases is due to the load (because of the higher pitch angle)   and not due to the pilot decrease the engine's RPM through throttle. They are very different.

With a constant speed propeller, the throttle only affects RPM when the prop is still at its fine pitch stop.  When there is enough power to exceed the RPM at which the governor is set, the governor starts regulating RPM by increasing pitch.  While the prop is on the governor, changing throttle position doesn't have an effect on RPM unless the throttle is reduced enough to cause the prop to hit its fine pitch limit.  This is something important to understand because at normal power settings something that reduces power (like carb ice) doesn't cause an RPM drop until its too late.

Thank you @John-K of your explanation. I now understand it after searching in youtube as well.

In the context of that discussion, it doesn't matter much whether it's the engine or propeller.
RPM is just a unit of measure, and you can apply it to anything that turns.
For the pilot, the prop speed is one of the most important parameters, so it is the prop RPM that is usually displayed.
Many, perhaps most small aircraft have 'direct drive' prop, where the engine shaft drives the propeller directly. Obviously, their RPM will be exactly the same.
Some have a gearbox (nearly always a reductor). In that case, as I said, usually the prop RPM are displayed, but because the engine and the prop are still hard-linked, the measurement can actually be made on the engine shaft and then recalculated.
Turboprops always have a gearbox. But added to that, they nearly always have two turbines (in each engine). One drives the prop, and it is normally linked to the gearbox just like a piston engine. So their RPM change together with the prop. But the other turbine drives the compressor and is more or less independent. And even though it doesn't affect the power directly, its RPM are also important and get displayed separately. But the pilots specifically mention that when they talk about this turbine.
So again, in the context of that discussion, the important points were how RPMs are changed. And they change together, they are hard-linked (lest there is a horrible failure): if one drops, the other does too. The numbers may be different if there is a gearbox, but who cares.
If you are still interested why things happen as they do, you can ask a separate question.